Time fuse for artillery projectiles



Jam. 20, 1942. 'p. KUNZ TIME FUSE FOR AR Filed Jan. "27, 1939 2 sheetsfisheet 1 361m 1941 P. A. KUNZ 2,270,534

TIME FUSE FOR ARTILLERY PROJECTILES Filed Jan. 2'7, 1959 2 Sheets-Sheet 2 Patented Jan. 20, 1942 UNIT TIlWE FUSEFOR ARTILLERY PROJECTILES Paul Albert Kunz, Le Locle, Switzerland Application January 27, 1939, Serial No. 253,207 In Germany and France February 21, 1938 3 Claims.

The invention relates to a mechanical fusefor artillery projectiles, having a timing gear in which moving masses serving to bring about ignition of the charge drive the timing gear under the action of centrifugal force, the masses moving in a spiral path lying in a paraboloidal or approximately conical surrounding surface up to the moment of direct actuation of the igniter. If there is only one such moving mass or if there are several such moving masses as hitherto in a common path, an unsymmetrical moving system with respect to the fuse axis is always produced, in the case of a single mass through lack of a counterbalance, in the case of several masses owing to the persistent difference in lever arm of one with respect to another due to thespiral course of the track, so that this unsymmetrical moving system during de-centring or secondary movements of the projectile suffers interference with its correct driving action.

The present invention seeks to overcome this fault by guiding several centrifugal masses used on the above lines, not in the same spiral track, but each in its own spiral track and in such a way that all are always at the same running level, so that the masses form a movin or drive system which is symmetrical to the axis of the projectile and the driving eifect of which remains unaffected by decentring or the like.

The accompanying drawings illustrate an example embodying the invention having for instance two spherical centrifugal masses.

Figure 1 is a view, partly in elevation and partly in longitudinal section, of the fuse.

Figure 2 shows a diagrammatic plan view of the spiral tracks or grooves, on a somewhat smaller scale than Figure 1.

Figure 3 shows a diagrammatic development of the spiral grooves for the two masses.

Figures 4 and 5 are views corresponding to Figures 2 and 3 of the known arrangement having a common spiral groove for the two masses.

Figure 6 is a diagram showing the driving torque relationship of the masses in the case of the invention.

The fuse body I (Figure 1) carries the timing gear 2, of which the first wheel is shown at 4. The timing gear 2 is driven by a conical driving wheel 6 of which a toothed rim 1 meshes with the wheel 4, and which is provided on its conical periphery with longitudinal grooves. The wheel 6 itself is driven by means of two moving masses in the form of balls 5a, 5b, which are guided by the grooves in the driving wheel 6, and under the action of centrifugal force run on a conical surrounding surface in the fuse body I, each in its own spiral groove I2, l3 respectively and always at exactly the same height or level as the other, so that the two masses or balls form a moving system exactly symmetrical to the axis of the fuse. At its upper end one of the spiral grooves communicates with an outward passage 8 into which the respective ball enters at the end of its movement and engages the firing pin 9 which has been retained in the usual way and which when it strikes the primer Ill ignites the explosive charge through the fire conduit II.

For setting the time of the fuse it suffices to turn the ogival cap 3 which is provided with a suitable time scale. This cap is connected with the timing gear 2 which is held friction tight in the fuse body I. Since the wheels and the escapement of the timing gear are before discharge of: the projectile locked in known manner by various locks arranged to be released by inertia and centrifugal effects, thewheel 4 moved bodily with the cap when the latter is turned, carries with it the toothed rim 1, the driving wheel 6 and the balls 5a, 5b, which are guided in the grooves of the wheel 6. Since the speed of rotation of the driving wheel 6 is regulated by the timing gear, the running time is proportional to the angle a (Figure 2) formed between the outward passage 8 and the ball 5a at the starting point, with the fuse axis as the vertex.

When the projectile is discharged the timing gear is released in known manner and set in motion through the driving wheel 6 by the balls 5a, 5b which from the starting point under the action of centrifugal force rise each in its own spiral groove I 2, l3 symmetrically opposite one another, thus constituting a symmetrical drive system with respect to the axis of the fuse, until the one of the balls passes into the passage 8. Figure 2 illustrates how the centrifugal force acting on the balls can be resolved into a component perpendicular to the groove and a driving component. The balls and their spiral tracks forming a drive system exactly symmetrical to the axis of the fuse, any shifting of the axis of rotation of the projectile will be without effect on the algebraic sum of the partial driving moments developed by the balls. Figure 6 explains this fact. In this figure the centres of the balls are indicated at 5 and 5 It is assumed that the projectile is decentred, that is instead of rotating about the axis A from which the two balls are equidistant at every corresponding point of their tracks, it rotates about some other axis, say A. Fa and Fb are then the centrifugal forces which act upon the respective balls 5 and 5 with A as the axis of rotation. Their magnitudes have been marked in proportion to the distance of the balls from the axis A (the balls have the same diameter and are identical in mass). The lines 5a--d and 513- are equal to the components fa and fb of the forces Fa and Fb, acting normally to the spiral tracks at the points of contact of the balls, and the components fa and fl; represent the driving forces perpendicular to the direction Sw-A and bA. If a perpendicular be dropped from A on to the line 5b--A5a, four triangles are formed, pairs of which are congruent, namely the triangles 5a, fa, Fa, and 5a, A, d on one hand, and 5b, fb, Fb

and 513A, c on the other hand. In the assumed example the decentring is such that the force fa is negative.

Nevertheless, the algebraic sum fa+,fb remains constant in all cases, also in case of an eventual decentring, and equal to the distance line a--b between the normals to the two spiral tracks, which is not the case for example with a common spiral track for all the balls as in Figure 4 since the balls on the track, as Figures 4 and 5 show, are at any instant at different radii, whereas with the separate spiral tracks according to the invention the balls at any instant meat the same level and therefore at the same radius as shown by the development in Figure 3.

Instead of the strictly spiral form for the grooves or tracks 12, I3 any other equivalent form can be used provided it expands spirally in its upward course.

What I claim is: t

1. In a mechanical fuse for an artillery projectile, the combination of a timing gear, a plurality of centrifugal masses in symmetrical circumferentially-spaced driving engagement with said timing gear, a separate upwardly-divergent guiding track for each of said masses,

ing tracks being at substantially the same radial distance from the projectile axis and in substantially the same plane normal to said axis, whereby a plurality of gear-driving systems disposed symmetrically of said axis is produced.

2. Ina mechanical fuse for an artillery projectile, the combination of a timing gear, a plurality of centrifugal masses in symmetrical circumferentially-spaced driving engagement with said timing gear, a separate upwardly-divergent guiding track for each of said masses, corresponding points on each of the several guiding tracks being at substantially the same radial distance from the projectile axis and in substantially the same plane normal to said axis, and

'means for retaining said masses in predetermined relative spacial arrangement While allowing movement thereof along their respective guiding tracks, whereby a plurality of gear-drivingsys tems disposed symmetrically of said axis is produced. I

3. In a mechanical fuse'for an artillery, projectile, the combination of a timing gear, a plurality of centrifugal masses in symmetrical circumferenti'ally -spac'ed driving engagement with said timing gear, a plurality of separate upwardly-diverging spiral guiding tracks, one for each said mass, corresponding points on each of the several guiding tracks being at substantially the same radial distance from the projectile axis and in substantially the same radial distance from the projectile axis and in substantially the same plane normal to said axis, and means for PAUL ALBERT KUNZ. 

